package cn.tml.innermost.music.utils;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
import java.util.Date;

/**
 * 多线程下载
 *
 */
public class ThreadDownloader {

    static String downLoadAddress = "/home/tml/project/music";
    //static String downLoadAddress = D:\\music\\";

    public static File urlGetFile(String urlStr) throws IOException, InterruptedException {

        // 记录开始下载的时间
        long begin_time = new Date().getTime();

        // 创建一个URL链接
        // 从hao123网站下载一个输入法，下面是下载地址
        URL url = new URL(urlStr);

        // 获取连接
        URLConnection conn = url.openConnection();

        // 获取文件全路径
        String fileName = url.getFile();
        fileName = fileName.split("\\?")[0];

        // 获取文件名
        fileName = fileName.substring(fileName.lastIndexOf("/"));
        // 获取文件大小
        int fileSize = conn.getContentLength();

        // 设置分块大小
        int blockSize = 1024 * 1024;
        // 文件分块的数量
        int blockNum = fileSize / blockSize;

        if ((fileSize % blockSize) != 0) {
            blockNum += 1;
        }

        Thread[] threads = new Thread[blockNum];
        for (int i = 0; i < blockNum; i++) {

            // 匿名函数对象需要用到的变量
            final int index = i;
            final int finalBlockNum = blockNum;
            final String finalFileName = fileName;

            // 创建一个线程
            threads[i] = new Thread(() -> {
                try {
                    // 重新获取连接
                    URLConnection conn1 = url.openConnection();
                    // 重新获取流
                    InputStream in = conn1.getInputStream();
                    // 定义起始和结束点
                    int beginPoint = 0, endPoint = 0;
                    beginPoint = index * blockSize;

                    // 判断结束点
                    if (index < finalBlockNum - 1) {
                        endPoint = beginPoint + blockSize;
                    } else {
                        endPoint = fileSize;
                    }
                    // 将下载的文件存储到一个文件夹中
                    //当该文件夹不存在时，则新建
                    File filePath = new File(downLoadAddress);
                    if (!filePath.exists()) {
                        filePath.mkdirs();
                    }

                    FileOutputStream fos = new FileOutputStream(new File(downLoadAddress, finalFileName + "_" + (index + 1)));

                    // 跳过 beginPoint个字节进行读取
                    in.skip(beginPoint);
                    byte[] buffer = new byte[1024];
                    int count;
                    // 定义当前下载进度
                    int process = beginPoint;
                    // 当前进度必须小于结束字节数
                    while (process < endPoint) {

                        count = in.read(buffer);
                        // 判断是否读到最后一块
                        if (process + count >= endPoint) {
                            count = endPoint - process;
                            process = endPoint;
                        } else {
                            // 计算当前进度
                            process += count;
                        }
                        // 保存文件流
                        fos.write(buffer, 0, count);

                    }
                    fos.close();
                    in.close();

                } catch (Exception e) {
                    e.printStackTrace();
                }
            });
            threads[i].start();
        }

        // 当所有线程都结束时才开始文件的合并
        for (Thread t : threads) {
            t.join();
        }

        // 若该文件夹不存在，则创建一个文件夹
        File filePath = new File(downLoadAddress);
        if (!filePath.exists()) {
            filePath.mkdirs();
        }
        // 定义文件输出流
        FileOutputStream fos = new FileOutputStream(downLoadAddress + fileName);
        for (int i = 0; i < blockNum; i++) {
            FileInputStream fis = new FileInputStream(downLoadAddress + fileName + "_" + (i + 1));
            byte[] buffer = new byte[1024];
            int count;
            while ((count = fis.read(buffer)) > 0) {
                fos.write(buffer, 0, count);
            }
            fis.close();
        }
        fos.close();
        return new File(filePath + "/" + fileName);
    }

}
